Method of boiling indirectly



R.H.HULT

METHOD OF BOILING INDIRECTLY.

APPLICATION FILED ocT.24.I9|7:

, Patented A r. 20, 1920.

2 SHEETS- SHEET I.

INVENfOm R. H.' HULT. METHOD OF B0lLl NG I NPIREGTLY. APPLICATION FILED on. 24, 191i.

Patented Apr. 20, 1920.

2 SHEETS-SHEET 2.

IN'VEN OR: R. H. HQLT UNITED sTArEs PATENT OFFICE.

ROLF HARALD HULT, OF HYLTEBRUK, SWEDEN.

METHOD OF BOILING INDIREC'I'LY.

Application'filed October 24, 1917.

I1 '0 all whom it may concern Be it known that I, ROLF HARALD HULT,

citizen of Finland, residing at Hyltebruk,

containing cellulose according to the sulfite method. The purpose of my present invention is to obtain a high economy of heat in the boiling operation, and, consequently, to save fuel.

The indirect boiling of a liquid by means of steam is generally executed, as is well known to those skilled in the art, by leading superheated or saturated steam through one or more metallic coils or tubes submerged in the liquid, the steam thereby giving off its heat to the liquid. The economy of such a method evidently depends on the quantity of heat given off to the liquid by the steam when passing through the coils or tubes, and a measure of the same is the difference of temperature between the incoming and the escaping steam, and water of condensation.

In the indirect boiling bysteam, especially at temperatures above the boiling point, one can. distinguish two different periods, namely a first period, during which the temperature of the liquid is raised from the ordinary temperature to or nearly to the boiling point, and a second period, during which the temperature is maintained at the boiling point or raised above the same. During the first period the consumption of steam is highest and the condensation in the coils is most complete. The economy of heat during this period is, even in the methods of heating employed hitherto, relatively good. During the second period, on the contrary, the economy has been very bad in the method employed hitherto, this being due to the fact that the heat of the steam, which has hitherto in each boiler been led the same way as during the first period, is utilized less completely and the condensation is less complete.

Patented. Apr. 20, 1920..

Serial No. 198.358.

steam, if wanted together with the water of condensation, is within one and the same boiler led a longer way through the liquid, so that the steam may act upon the liquid for a longer time and more completely deliver its heat to the same. i r Another object of my invention consists in applying said method to the sulfite cellulose method so that during the first period (when the temperature is raised from ordinary temperature to about 100 to 105 C.) the steam is led through the coils or tubes being then in the ordinary manner coupled parallelly, and then during the second period of the boiling operation (generally between about 105 to about 138 C. or more) the coils or tubes are coupled in series two and two, three and three etc, and the steam led through the coils or tubes thus coupled together in series.

Another feature of my invention consists therein that, during the second period, the main valve of the outlet conduit for the escaping steam is throttled to a suitable degree for increasing the favorable action of I example the application of the invention in boiling wood according to the sulfite cellulose method, reference being had to the Fig. 3 illustrates an arrangement which inlet and outlet valves.

In the indirect boiling of sulfite cellulose superheated or saturated steam, mixed if wanted with water of condensation, is led through coils of lead or copper located in the lower part of the boiler. These coils have hitherto generally consisted of a number of independent coils arranged in the manner indicated by Fig. 1. The coils, generally four to six, are designated by A, B, C, D and E. One end of each coil is connected with the main supply conduit of steam F connected with the main conduit G for through the outlet. conduit.

\escaping steam by means of the connecting tubes a, b 0 d and e In the boiling operation the steam passes according to the hitherto employed method the same wa during the first as during the second perio for instance, as regardsthe first spiral, the following way: F, a, A, a G.

The economy of the'boiling is however, as stated above, to a high degree depending on the temperature of the escapingsteam, and water of condensation, the latter being no doubt employed within the factory, although it can seldom be fully utilized.

In order to obtain a better economy in the boiling operation one now proceeds ac 'cording to my present invention in the manner that the steam, mixed if necessary with Water of condensation, is during the second period made-to pass a longer way through the liquid so that it may act upon the liquid for a longer time. This result can be obtained in several manners, for instance by using the arrangement of the tubes shown in Fig. 2. According to this figure the coils may, by the use of connecting tubes and suitably located valves or'other throttling arrangements, be coupled either in parallel so that the steam passes the same way as in Fig. 1, or in series so that the steam is made to pass through two coils before escaping Accordin to Fig. 2 six coils are used, namely H, I, K, L and M, which are by the conduits k, i, j, if, Z and m respectively connected with the main steam supply conduit N. The outlet ends of the coils are by the conduits 7L 2' j Z and m connected with the main steam outlet conduit O. The conduits i and k are connected with each other by a tube w. The conduit 2' is by a conduit lconnected with the inlet end of the coil I, and the outlet end ofcoil H is by a conduit 2 connected with conduit h On both sides of the orifices of the conduits 1 and 2 there are located valves 3, 4 and 5, 6 respectively. In the same manner the conduit is is connected with the conduit j by a connecting tube 3 The conduit is is by a conduit 7 connected with the inlet end of coil K, and the outlet end of coil J is by the conduit 8 connected with-the conduit j On each side of the orifices of the conduits 7 and 8 there are located valves 9,10 and 11, 12 respectively. Moreover, the conduit m is connected with the conduit Z by a connecting tube 2. The conduit m is by a conduit 13 connected with the inlet end of coil M, and the outlet end of the coil L is by a conduit 14 connected with the conduit Z On each side of the orifices of the conduits 13 and 14 there are located valves or other throttling devices 15, 16 and 17, 18 respectively.

During the first period of the boiling operation (i. 6. while the temperature is raised to about 100 to 105 O.,. these figures are only approximate and the invention is not limited to the same) when the consumption of steam is highest and the condensation in c the coils most complete, the coils are in the ordinary manner coupled in parallel. The way of the steam will then through the first coil be the following: N, h, H, 2, k O and through the second coil: N i, Z, I, '5 O, and so on for the other coils. The valves 3, 9, 15, 6, 12 and 18 are then open, while the valves 4, 10, 16 and 5, 11,- 17 are shut. Hereby the desired rapid raising of the boiling is obtained, without loss of steam. During the second period (from 100 or 105 C. and upward) when the boiling is getting easier, at the same time as the condensation becomes less complete, the coils are coupled two and two in series, so that one, instead of six short coils, obtains three long ones. This coupling in series is obtained by shifting the said valves, so that -next two coils the steam passes as follows:

N, j, J. 8, o 7, K, 71: O, and through the last coils N, Z, L, 14, z, 13, M, 111., O.

The result obtained by leading the steam in this manner during the second period is that the escaping steam has a considerably lower temperature in comparison with the corresponding period in the method hitherto employed. The higher the temperature then raises in the boiler the more the steam admission valve is throttled, and finally, when the maximum temperature (generally about 138 C.) has been reached, the steam alcllmission valve can often be completely s ut.

It is evident, that the arrangement according to Fig. 2, is shown and described as an example only and may, consequently, be varied within wide limits without departing from the scope of the present invention. Thus, it is not necessary to couple the coils in series two and two, but the coils may when this is convenient be coupled together three and three, four and four, etc. If for instance the coils are to be coupled three and ond and third, the fourth and fifth, the fifth and sixth coils are, as is schematically illus trated in Fig. 3, combined with connecting tubes m 413 7 3 in such a manner that the outlet end of the first coil H and the inlet end of the second coil I can be put in communication with each other by a connecting tube :0 and the outlet end of the second coil I can be put in connection with the inlet end of the third coil J by means of the next congroup. As the valves are located and act in an analogous manner to that described in connection with Fig. 2 it ought to be unnecessary to repeat the description here.

The arrangement for coupling together the coils can of course be varied within wide limits. It is, thus, not necessary to use connecting tubes, for instance :0, y, z in Fig. 2. This can be rendered possible by directly coupling together the valves 4 and 5, 10 and.11, 16 and 17. This arrangement is schematically illustrated in Fig. 4; showing the lower part of a boiler in elevation. In order to avoid confusion the coils H, I, J, K, L, M within the boiler are not shown. It is, however, easy to understand that the inlet end of the coil H is connected with the conduit h and the outlet end with the conduit k etc. During the first period the steam will. pass the following way through the first coil: N, h, H, 79, 6, O, the valves 4, 5 being shut and the valve 6 open. In an analogous manner the steam passes through each of the other coils. During the second period, when the coils are coupled in series two and two,

the steam will pass the following way through the first couple of coils: N, h, H, M, .3, 4:, i, I, 5 O, the valves 6 and 3 being shut and t and 5 being open, and so on for the other couples of coils,

Fig. 5 schematically shows another arrangement, which is a combination of series and parallel coupling. the principal object of which is to reduce the number of valves. The coils are here adapted to be coupled together in series three and three during the second period. During the first period the steam passes the same Way as described in connection with Fig. 4, the valves 4 and 16 being then open and valve 10 shut. During the second period the valves 4: and 16 are shut and valve 10 open, and the steam then passes through theroups of coils as follows: Nh, z, jH, I, h 2' j 10k, Z, mK, L, M-Jrfi, Z, m

To assure that the steam shall pass or be guided as desired, -there may be used, instead of single principal valves, such as 4, 10 and 16, in Fig. 5, double principal valves, and to locate testing valves between the latter, by the opening of which it is quite possible to ascertain the path of the steam at any time during the boiling operations,

and to also ascertain whether the valves are tight. Such an arrangement is schematically shown in Fig. 6, Where the double principal valves are indicated at S 8,, T T and U U The testing valves (located between the double principal valves) are in.-

dicated at P P, and P respectively. During the first period, the valves S, and 8,, U, and U remain open, While valves T and T. are closed, and it is then possible to make certain that the steam passes as desired, by opening testing valves P,, P, and P in whichcase steam will escape from P and P but not from P,. During the second period, valves S S and U,U remain shut, while T and T remain open. Upon opening the testing valves, steam will then escape from P but not from P, or P The present invention also comprises the above described arrangements which can be used in carrying out the method.

Finally it may be mentioned that I am aware of the fact that, in sulfite cellulose factories with several boilers, it has been proposed to lead the steam escaping from a boiler into the coils of the next boiler for utilizing it there as heating steam instead of fresh steam. According to this known system however, the coils in each boiler are in the ordinary manner coupled parallelly both during the first and the second period, and it is only the different boilers that are coupled in series.

It is also known that one has tried to improve the economy of heat during the second period partly by throttling the main valve of the steam outlet condult and partly by locatin at the said place anoutlet for water of con ensation' Neither the one nor the other of these known systems anticipates the present invention as the latter is based on leading the steam in one and the same boiler different ways during both the periods of the boiling operation, so that the steam is during each period utilized in the most favorable manner. coils that they can during the first period be coupled parallelly and during the second period in series. In combination with this general arrangement one can of course within certain limits regulate the result by throttling to a suitable degree the main valve on the outlet side during the second period, and one may also, if desired, on said side locate an outlet for water of condensation.

The advantages obtained by the present invention as compared with the methods hitherto employed evidently consist in making possible as well a rapid raising of the temperature of the liquid toor nearly to the boiling point, as a better utilizing than hitherto of the steam during the continuation of the boiling operation.

This is obtained by so combining the The expression first period of the boiling of the temperature above the boiling point and the maintaining of av desired tempera ture if the boiling takes creased temperature.

' Instead of steam any other heating agent may be employed.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. The method of indirectly boiling liquid, consisting in first leading a heating agent place under an inthrough each of a plurality of parallellysubmerged in said liquid.

3. The method of indirectly boiling liquid, consisting in first leading a heating agentthrough each of a plurality of parallellycoupled heating elements submerged in said liquid, and until the temperature of said liquid is raised to about the'boiling point,

and then leading a heating agent through serially-connected heating elements submerged in said liquid, and raising the temperature of the latter to any desired point above the boiling point.

4:- The method of indirectly boiling liquid consisting in first leading steam together with water of condensation through each of a plurality of parallelly-coupled heating pipes submerged in said liquid, and until the temperature of said liquid is raised to about the boiling point, and thereafter connecting said heating pipes in series and leading steam together with Water of condensation. through said serially-connected pipes, until the temperature of the liquid is raised to any desired point above the boiling point.

5. The method of indirectly boiling lyeliquid in the manufacture of sulfite cellulose, consisting in first leading a heating agent through each of a plurality of parallelly-coupled heating elements submerged in said liquid, and until the temperature has been raised to about IOU-105 0., and then connecting said heating elements in series and leading a heating agent through said serially-connected elements until the temperature of the liquid has been raised to about 138 C.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

ROLF HARALD HULT. Witnesses:

AxEL EHRNER, ERNST EHRNER. 

